This invention relates to an air bag device for protecting a passenger in a vehicle.
An air bag device generally has a case installed in a front panel part of the passenger compartment of a vehicle, such as an instrument panel or the middle of a steering wheel, an air bag received inside the case in a folded state, and an inflator, which is a gas generator. An air bag device is constructed so that in the event of a vehicle collision the air bag is inflated toward the passenger side by gas generated by the inflator and catches the body of the passenger.
To control the deployment behavior of the air bag in this kind of air bag device, JP-B-07090744 discloses an air bag device of which the case is disposed in an instrument panel so as to open upward, the inflator is disposed in the front side of the case, the gas delivery opening of the inflator is disposed in a position more to the front side, and a front side part of the folded air bag is disposed above this gas delivery opening, and as a result of this, when the air bag deploys, this front side part of the air bag is expanded first and the air bag is expanded progressively and freely thereafter.
However, when the gas delivery opening of the inflator is merely disposed nearer front of the inside of the case with a construction wherein a front side part of the folded air bag is disposed above this gas delivery opening as described above, the state of the part of the air bag positioned above the gas delivery opening varies depending on the state of folding and packing of the air bag and has an influence on the deployment behavior of the air bag. Consequently, there has been the problem that it is difficult to control the deployment behavior of the air bag.
In air bag devices of the kind described above, as the arrangement of the inflator and the air bag when the two are installed inside the case, conventionally there have been the series arrangement type shown in FIG. 23 and the parallel arrangement type shown in FIG. 24.
In the series arrangement type shown in FIG. 23, a cylindrical inflator 102 is disposed at the bottom of a case 101 which opens upward, and an air bag 103 is packed on the side of the opening at the top of the case 101.
In the parallel arrangement type shown in FIG. 24, a cylindrical inflator 102 is disposed in the side nearer the front of the vehicle of an upwardly opening case 101, i.e. in the side further from the passenger, and an air bag 103 is packed in the side nearer the rear of the vehicle, i.e. the passenger side.
In the series arrangement type described above, because the air bag 103 and the inflator 102 are disposed in a vertical direction, although it is possible to make the area of the opening in the case 101 small, because the whole of the air bag 103 is pushed out by the gas generated by the inflator 102 it is not easy to control its deployment behavior.
In the parallel arrangement type, because the inflator 102 and the air bag 103 are disposed in a horizontal direction, although the gas generated by the inflator 102 can be made to deploy the air bag 103 from the upper part side thereof, because the area of the opening in the case 101 is large there are many restrictions on the installation of the air bag device in a vehicle.
In the air bag device disclosed in JP-B-07090744 as described above, by disposing a front part of the folded air bag above the inflator, i.e. on the side of the case opening, it is possible to make the area of the case opening smaller than in the above-mentioned parallel arrangement type. However, when the air bag is simply packed extending from the case opening side of the inflator to the passenger side like this, as described above, depending on the state of folding and the state of packing of the air bag, good deployment behavior is not always obtained.
As the above-mentioned inflator, substantially cylindrical ones are known and are used in air bag devices such as those for passenger seat use. In recent years, substantially cylindrical inflators of a hybrid type, charged with high-pressure gas, have been being used. In an inflator of this hybrid type, because a gas blowout part is disposed at one end of the inflator, a diffuser is disposed between the inflator and the air bag to regulate the flow of the gas being fed into the air bag from the inflator. For example constructions such as providing one gas delivery opening in the middle of the diffuser to guide the gas into the middle of the air bag or making a gas delivery opening in the diffuser on the side of the gas blowout part of the inflator small and a gas delivery opening in the diffuser on the opposite side large to balance the amounts of the gas guided into the air bag flowing to the left and right are employed.
Thus, diffusers of the related art have been disposed in order to guide gas into the air bag uniformly in the width direction thereof, and have not positively controlled the shape of the air bag during its deployment by means of their gas delivery openings. Because of this, in air bag devices of the related art, to control the deployment behavior of the air bag, tear seams and tethers have been provided on the air bag itself, and consequently there have been problems such as that the package volume of the air bag is large and that the air bag is expensive.